A lens barrel is known which holds an optical system capable of changing its focal length. The lens barrel of this type moves a first lens group in the optical axis direction with respect to a first moving cam ring, by means of the first moving cam ring and a first group lens barrel. In the first moving cam ring, cam grooves are formed. The first group lens barrel has follower pins engaging with the cam grooves, and holds the first lens group (see Japanese Patent Unexamined Publication No. 2007-219304 and Japanese Patent Unexamined Publication No. 2002-90611, for example).